WASHINGTON (Reuters) - Washington's last-minute scramble to step back from a recession-inducing "fiscal cliff" shifted to the Republican-controlled House of Representatives on Tuesday after the Senate approved a bipartisan deal to avoid steep tax hikes and spending cuts.

In a rare late-night show of unity, the Senate voted 89 to 8 to raise some taxes on the wealthy while keeping income taxes low on more moderate income voters.

The bill's prospects were less certain in the House, where a vote had not yet been scheduled. Many conservative Republicans have rejected tax increases on any Americans, no matter how wealthy. Some liberal Democrats were also upset with a complex deal that they thought gave away too much.

Lingering uncertainty over U.S. tax and spending policy has unnerved investors and depressed business activity for months, and lawmakers had hoped to reach a deal before Tuesday, when a broad range of automatic tax increases and spending cuts would begin to punch a $600 billion hole in the economy.

Financial markets have avoided a steep plunge on the assumption that Washington would ultimately avoid pushing the country off the fiscal cliff into a recession.

With financial markets closed for the New Year's Day holiday, lawmakers have one more day to close the deal.

"My district cannot afford to wait a few days and have the stock market go down 300 points tomorrow if we don't get together and do something," Representative Steve Cohen, a Democrat from Tennessee, said on the House floor.

The bill passed by the Senate at around 2 a.m. would raise income taxes on families earning more than $450,000 per year. Low temporary rates that have been in place for less affluent taxpayers for the past decade would be made permanent, along with a range of targeted tax breaks put in place by President Barack Obama in the depths of the 2009 recession.

However, workers would see up to $2,000 more taken out of their paychecks as a temporary payroll tax cut was set to expire.

The bill would also delay an across-the-board 8 percent spending cut to domestic and military programs for two months, and extend jobless benefits for 2 million people who otherwise would see them run out.

Obama in a statement on Monday urged the House to vote. "There's more work to do to reduce our deficits, and I'm willing to do it," he said.

Republicans had hoped to include significant spending cuts in the deal to narrow trillion-dollar budget deficits. Conservatives were already looking forward to the next battle over the debt ceiling, in late February, to extract deficit reduction measures from the Democratic president.

Vice President Joe Biden, who was instrumental in pushing through the Senate measure, was scheduled to address a closed-door meeting of House Democrats. Their support likely will be needed to pass the bill.

Republican members were to meet to discuss "a path forward," a senior aide said.

The meeting could help Republicans leaders decide when to begin consideration of the White House-backed measure. A vote could come later in the day, but was not yet scheduled.

The conservative Club for Growth urged a "no" vote on the Senate measure, saying it would be on its "congressional scorecard" used to challenge members of Congress.

Liberal groups also have urged Democrats to reject the deal.

Richard Trumka, head of the AFL-CIO labor union, wrote on Twitter that the deal does not raise taxes enough on the wealthy and "sets the stage for more hostage taking" by Republicans in future budget confrontations.

Republican Representative Tom Cole said his House colleagues should pass the Senate bill rather than try to change it.

"We ought to take this deal right now, and we'll live to fight another day," Cole said on MSNBC. "Putting to bed this thing before the markets (open on Wednesday) is really a pretty important thing to do."

WASHINGTON (Reuters) - The Senate moved the U.S. economy back from the edge of a "fiscal cliff" on Tuesday, voting to avoid imminent tax hikes and spending cuts in a bipartisan deal that could still face stiff challenges in the House of Representatives.

In a rare New Year's session at around 2 a.m. EST (0700 GMT), senators voted 89-8 to raise some taxes on the wealthy while making permanent low tax rates on the middle class that have been in place for a decade.

But the measure did little to rein in huge annual budget deficits that have helped push the U.S. debt to $16.4 trillion.

The agreement came too late for Congress to meet its own deadline of New Year's Eve for passing laws to halt $600 billion in tax hikes and spending cuts which strictly speaking came into force on Tuesday.

But with the New Year's Day holiday, there was no real world impact and Congress still had time to draw up legislation, approve it and backdate it to avoid the harsh fiscal measures.

That will need the backing of the House where many of the Republicans who control the chamber complain that President Barack Obama has shown little interest in cutting government spending and is too concerned with raising taxes.

All eyes are now on the House which is to hold a session on Tuesday starting at noon (1700 GMT).

Obama called for the House to act quickly and follow the Senate's lead.

"While neither Democrats nor Republicans got everything they wanted, this agreement is the right thing to do for our country and the House should pass it without delay," he said in a statement.

"There's more work to do to reduce our deficits, and I'm willing to do it. But tonight's agreement ensures that, going forward, we will continue to reduce the deficit through a combination of new spending cuts and new revenues from the wealthiest Americans," Obama said.

Members were thankful that financial markets were closed, giving them a second chance to return to try to head off the fiscal cliff.

But if lawmakers cannot pass legislation in the coming days, markets are likely to turn sour. The U.S. economy, still recovering from the 2008/2009 downturn, could stall again if Congress fails to fix the budget mess.

"If we do nothing, the threat of a recession is very real. Passing this agreement does not mean negotiations halt, far from it. We can all agree there is more work to be done," Majority Leader Harry Reid, a Democrat, told the Senate floor.

A new, informal deadline for Congress to legislate is now Wednesday when the current body expires and it is replaced by a new Congress chosen at last November's election.

The Senate bill, worked out after long negotiations on New Year's Eve between Vice President Joe Biden and Senate Republican Minority Leader Mitch McConnell, also postpones for two months a $109 billion "sequester" of sweeping spending cuts on military and domestic programs.

It extends unemployment insurance to 2 million people for a year and makes permanent the alternative minimum tax "patch" that was set to expire, protecting middle-income Americans from being taxed as if they were rich.

'IMPERFECT SOLUTION'

The tax hikes do not sit easy with Republicans but conservative senators held their noses and voted to raise rates for the rich because not to do so would have meant increases for almost all working Americans.

"It took an imperfect solution to prevent our constituents from a very real financial pain, but in my view, it was worth the effort," McConnell said.

House Speaker John Boehner - the top Republican in Congress - said the House would consider the Senate deal. But he left open the possibility of the House amending the Senate bill, which would spark another round of legislating.

"The House will honor its commitment to consider the Senate agreement if it is passed. Decisions about whether the House will seek to accept or promptly amend the measure will not be made until House members ... have been able to review the legislation," Boehner and other House Republican leaders said in a statement.

Boehner has struggled for two years to get control over a group of several dozen Tea Party fiscal conservatives in his caucus who strongly oppose tax increases and demand that he force Obama to make savings in the Medicare and Social Security healthcare and retirement programs.

A campaign-style event held by Obama in the White House as negotiations with Senate leaders were taking place on Monday may have made it more difficult for Republicans to back the deal. In remarks to a group of supporters that resembled a victory lap, the president noted that his rivals were coming around to his way of seeing things.

"Keep in mind that just last month Republicans in Congress said they would never agree to raise tax rates on the wealthiest Americans. Obviously, the agreement that's currently being discussed would raise those rates and raise them permanently," he said to applause before the Senate deal was sealed.

Obama's words and tone annoyed Republican lawmakers who seemed to feel that the Democrat was gloating.

"That's not the way presidents should lead," said Republican Senator John McCain, Obama's rival in the 2008 election.

A deal with the House on Tuesday, while uncertain, would not mark the end of congressional budget fights. The "sequester" spending cuts will come up again in February as will the contentious "debt ceiling," which caps how much debt the federal government can hold.

Republicans may see those two issues as their best chance to try to rein in government spending and clip Obama's wings at the start of his second term.